Multiple input, multiple output (MIMO) is a wireless communication technique that uses multiple antennas at each end of a communication channel. That is, a transmitting device uses multiple transmit antennas to transmit signals into one end of the wireless channel and a receiving device uses multiple receive antennas to receive the signals at the another end of the wireless channel. By using multiple antennas at each side of the channel, the spatial dimension can be taken advantage of in a manner that improves overall communication performance. MIMO can be implemented as an open loop or a closed loop technique. In open loop MIMO, a transmitting device does not have any knowledge of the state of the channel before transmitting a signal into the channel. In closed loop MIMO, on the other hand, the transmitting device acquires and uses channel related information (e.g., a beamforming matrix, etc.) to precondition signals before transmitting them into the channel. Techniques are needed for efficiently training MIMO channels during closed loop MIMO operations.